Sunstone is known for exhibiting a captivating optical phenomenon called schiller or aventurescence, which appears as tiny shimmering sparkles when the stone is moved under light. But where in the world can you go to find this visually dazzling gemstone?
The Origin of Sunstone
Sunstone forms through the slow cooling and solidification of molten lava rich in sodium, calcium, aluminum, and silica. As the molten material cools, intergrown alkaline feldspar and plagioclase feldspar crystals develop. Tiny hematite platelets also become embedded within the feldspar matrix during crystallization, producing the schiller effect for which sunstone is prized.
The sunstone deposits we mine today were formed millions of years ago from ancient lava flows that have long since cooled and left extensive sunstone-bearing pegmatites and basalt flows across the earth's surface. While sunstone is found in limited localities worldwide, a few countries hold the most significant deposits of gem-quality material.
Norway
The most important source of natural sunstone has long been Norway. Deposits of sunstone are found mainly in an area called Sunnmøre, which encompasses several islands along the western coast of the Scandinavian country. Precambrian bedrock in this region contains veins of fine-quality sunstone that have been mined here for over a thousand years. Skilled Viking craftsmen adorned their jewelry and tools with locally mined sunstones, prizing them for their beauty. Today, Norway remains the premier source for natural sunstone of premium color and clarity.
Oregon, USA
While not as well known as Norwegian sunstone, Oregon produces the majority of sunstone mined in the United States today. Deposits are located mainly in Lake and Harney counties of southeastern Oregon. Here, ancient basalt lava flows harbored pockets of sodium-rich molten rock ideal for sunstone formation. The Ponderosa Mine in Lake County has been the most productive sunstone deposit, providing stones exhibiting deep red and orange hues. Oregon sunstone is also frequently treated to enhance color and remove undesirable mineral inclusions.
India
Several states across India, including Uttar Pradesh, Jammu & Kashmir, Madhya Pradesh, Maharashtra, and Odisha, contain sunstone deposits. These occurrences are associated with pegmatites related to the Deccan Traps lava flows that covered parts of central India during the Cretaceous period. Indian sunstones can display beautiful deep red, orange, and green tones but are often more opaque than fine Norwegian and Oregon material. However, Indian sunstones frequently exhibit striking cat's eye chatoyancy when cut as cabochons.
Russia
Russia has long been known for its mineral wealth, including gem-quality sunstone. Significant deposits are found along the shores of Lake Baikal in southern Siberia. Russian sunstone occurs in granitic pegmatites and exhibits characteristic schiller inclusions. While Russian material can occasionally be of fine quality, most production is lower grade, opaque stones best suited for mass-market carvings and new age metaphysical purposes. However, sources around Lake Baikal have the potential to yield rare natural alexandrite-like crystals that change from red to green depending on lighting conditions.
So, while sunstone deposits occur globally, the premier sources for top-grade transparent material are Norway, Oregon in the US, and certain deposit in India. From jewelry to carvings, sunstone's unique visual properties continue to captivate gem enthusiasts and artisans worldwide.
